Method of preparing aliphatic fluorine compounds



United States Patent METHOD on PREPARING ,ALIPHATIC FLUORINE comrounns Otto Scherer, Helmut Hahn, and Heinrich Kiihn, Frankfurt am Main, Germany, assignors to Farbwerke Hoechst Aktiengesellschaft vormals Meister Lucius 8: 'Briining, Frankfurt am Main, Germany, acorporation of Germany e No Drawing. Application Tannery 23, 1957 7 Serial masseuse Claims priority, application Germany February 3, 1956 6 Claims. (Cl. 2609-6535 This'invention relates tofluorine containing aliphatic compounds and their preparation.

The'preparation of aliphatic fluorine compounds from 2,927,948 Fatented Mar. ,8, 1960 reaction conditions It has been found experimentally, for instance, that practically 'no corrosion of the aluminum vessels can batches while the aforementioned materials are so extensively attacked even after 50-60 batches that they must be replaced.

As antimony catalysts, there can be used antimonous halides in the presence of elemental chlorine as well as antimonic halides.

For instance, in an aluminum vessel there are obtained from 5 parts by weight hexachloroethane and 1 part by weight of a trivalent antimony halide, for instance, SbF- with the addition of a small quantity of elemental chlorine, :a good yield of a mixtureof tetrafluorodichloroethane and trifluorotrichloroethane.dcpending on the quantitypf'the hydrogen fluoride employed. The original catalyst retains its activity for a large num I berof batches. -When using trivalent antimony compounds, it is sufficient to add a small quantity'of elementalchlorinebeforeeach batch. Under the above conditions, trifluorodichloroethanc and difluorotrichloroethane are'obtained from pentachloroethane depending on the "quantity of the hydrofluoric acid used. This clearly demonstrates that aluminum strongly activates the fluorination reaction. 7

It has additionally been found that the reaction can be still rfurtheryactivated by adding a small quantity of instance trifiuorotrichloroethane, in the presence of a a.

large, for instance five times, excess of a catalyst consisting primarily of pentavalent antimony compounds (Example 19).; In accordance with'a method described in U.S. Patent No. 2,146,725, there is required a large quantitative excess not only of antimony catalyst but also of elemental Ichlorine usingva temperature of 160-165 C. w, e

Also in the,,case of the-method 10f U.S. Patent 'No. 2,658,927 (Example 1), despite the use of relatively large quantities of antimony pentachloride, substantially only trifluorotrichloroethane is obtained from hexachloroethane.

One can also operate with small quantities of antimony catalyst (French Patent No. 1,069,872), but in such case, in the above mentioned temperature ranges, there is obtained, for instance from pentachloroethane, only the monofluoro derivative. conditions (260 difluorotrichloroethane isobtained.

It is an object of this invention to provide a process for conducting fluorination reactions efficiently.

It is another object of this invention to provide a process for preparing highly fluorinated aliphatic compounds from the corresponding chlorinated aliphatic compound in high yields.

Various other objects and advantages will become apparent to those skilled in the art on reading the accompanying description and disclosure.

It has now been found that fiuorination reactions, using antimony catalysts can be strongly activated if the reaction is carried out in the presence of aluminum, e.g., in an aluminum vessel. This additional activation can also be noted from the accelerated course of the reaction and the relatively low reaction temperatures.

The use of aluminum vessels has not only the advantage that the reaction is activated but also the advantage Even when employing extreme C., 110 atm. gauge, 21 hours) only" an arsenic halide such .as arsenic trichloride and arsenic trifluoride tothe antimony halide. The addition o'f the arsenic-halide can bet-accomplished by boiling out the reaction vessel, for instance the autoclave, with the arsenic halide,- e'.g., arsenic htrifluoride, before use in order to assure the,activation ofaelarge number of batches. However, ;best results are, obtained when between about 0.1 andabout 10% .arsenichalidebased on the quantity'of thefantimony catalyst is added to each batch. The yield of higher fluorinated products is in this way considerably increased.

- l'n'order to illustrate thciprocesszof this invention, the following; examples, which are not to be construed as unnecessarily limiting, are presented.

Example 1 In a 30 liter aluminum autoclave, 20 kg. pentachloroethane and 5.5 kg. hydrofluoric acid are heated in'the presence of 3.5 kg. antimony trifiuorideand 200 grams of chlorine at -150 C. Under these conditions, the pressure rises to 50 atm. gauge. The hydrochloric acid formed is blown 01f over the course of 10-15 hours via a high pressure valve. The fluorine compounds produced are distilled out of the autoclave. There is obtained 48% of the theoretical yield of trifluorodichloroethane and 43% of the theoretical yield of difluorotrichloroethane.

Example 2 there is obtained upon distillation 39% of the theoretical yield of tetrafiuorodichloroethane (Freon 114) and 51% of the theoretical yield of trifluorotrichloroethane (Freon 113).

Example 3 2,370 grams of hexachlorethane are heated in the presence of 450 grams of antimony trifluoride (500 grams SbCl and grams HF),'850 grams HF and 30 grams chlorine as well as 45 grams arsenic trichloride at 130- be observed even after about 100 1 135 C. in an aluminum vessel. Under these conditions the pressure increases to 50-60 atmospheres gauge. The hydrochloric acid formed is let off in five hours. The distillation of the reactionproducts gives 78% of the theoretical amount of te't'rafluorodichlorethane together with "16% of the theoretical'amount of trifluorotri chlorn' Example 4 i (a) A closed, pressure-resistant aluminum vessel is filled w th 750 grams of antimony trifluoride 1275 grams of methylene chloride (15 mols) 720 grams of hydrogerrfluoride and 5 grams of chlorine.

At a temperature of 120 130" C. the pressure increases rapidly to 4 0 -50 atmospheres The hydrogen chloride and methyienefluoride formed are slowly withdrawn. Atterdegassing fora period of about 8 hours methylene fluoride is obtained in'a yield of 720 grams corresponding to 92% of the theoreticalamount. The compound Obtained boils at l C.

.(b) The conditions are the same with the exception, however, that an iron, pressure-resistant vessel is used. After degassing for 14 hours, methylene fluoride is obtained in a yield of only 520 grams corresponding to 67% of the theoretical amount.

Example 5 (a) A closed aluminum vesselinto which were previously introduced500 grams of antimony'trichloride, is filled with 1052 grams of trichlorethylene (8 mols), 600 grams of hydrogenfluoride and 50 grams of chlorine. At a temperature of 130 C., the pressure increases rapidly to about 50 atmospheres gauge. The hydrogen chloride formed and the reaction product'ar e slowly withdrawn through a high pressure 'valve. After degassing for 8 hours, there are obtained 785 grams of-1.1.1-trifiuorethyl chloride corresponding to a theoretical yield of 83%. The compound boils at +6 C.

(a) The conditions are otherwise the same with the exception, however, that an ironvessel is used. 1.1.1- trifluorethyl chloride is obtained in a poor yield 'and 4 varying quantities. The product obtained consists essentially of 1.1-difiuoro-l.Z-dichlorethane. The optimum yield in 1.1.l-trifiuorethyl chloride is 30-40% of the theoretical value.

In a manner analogopstothat described above there may also be reacted 1,2-dichlorethylenc,2-fluoroheptachloropropane and 1.23.4 tetrafluoroheigaehlorobutane.

Various modifications-and alterations of the process of this invention will be apparent to those skilled in the art and may beused without'departing from the scope of'this invention."

We claim: I Y

1. A'method for preparing a highly fluorinated aliphatic compound which comprises the single step of fluorinating a chlorinated hydrocarbon with hydrogen fluoride in the presence of aluminum, elemental chlorine, and a catalyst consisting esssentially of antimony trihalide admixed with between about 0.1 and about 10 percent by weightbf arsenic trihalide.

The method of claim 1 wherein the antimony trihalide'is antimony triflu'oride.

3. The metliod of claim 1 wherein the arsenic trihal ide" is selected fromtlie group consisting of arsenic trichloride'and arsenic trifluoride.

' 4. 'A meth'od for preparing a highly fluorinated aliphaticcompound which "comprises'the single step of fliiorinating achlorinated alkane with hydrogen fluoride ata r'hp'erat ure between about -135 C. in the presencefifaiuminum, elemental chlorine, and a catalyst ing' es'sentiallyfof antimony 'trifluoride admixed Ween about 0.1 and about 10 percent byweight of ar s enic 'trichloride.

,5; The method of claim 4 wherein the chlorinated alkane is pe'ntachloroethane- 6'. Theniethod of claim 4 M wherein the chlorinated al ies?i'ith xaahl t t an References Cited in the file ofthis patent UNITED STATES PATENTS 2,005,710 Daudt et a1 June 18, 1935 2,549,988 Perkins Apr. 24, 1951 2,757,213 Colfmant a1. July 31, 1956 2,768',98 3 Couperet a1. Oct. 30, 1956 

1. A METHOD FOR PREPARING A HIGHLY FLUUORINATED ALIPHATIC COMPOUND WHICH COMPRISES THE SINGLE STEP OF FLUORINATING A CHLORINATED HYDROCARBON WITH HYDROGEN FLUORIDE IN THE PRESENCE OF ALUMINUM, ELEMENTAL CHLORINE, AND A ATALYST CONSISTING ESSENTIALLY OF ANTIMONY TRIHALIDE ADMIXED WITH BETWEEN ABOUT 0.1 AND ABOUT 10 PERCENT BY WEIGHT OF ARSENIC TRIHALIDE. 